Magnéli phase Ti 4 O 7 with high electronic conductivity showed great promise as an inactive component of S cathodes that mitigates some intrinsic limitations of ultra-lightweight lithium-sulfur batteries (LSBs) based on low-cost, high specific capacity and largely environmentally benign sulfur (S). Here we report for the first time a straightforward and economic approach to synthesize mesoporous Magnéli phase Ti 4 O 7 microspheres by simply heating a mixture of elemental titanium and TiO 2 in argon. The phase-controlled method utilizes the mildest synthesis conditions to-date with lower temperature and exclusion of flammable hydrogen gas traditionally used, and also avoids generation of exhaust greenhouse gases during carbothermal synthesis using sacrificial polymers. The produced S/Ti 4 O 7 composite cathode with 70 wt% S loading efficiently mitigated the shuttle effect by both chemical adsorption and physical trapping of polysulfides. Consequently, this cathode showed high (88%) first cycle columbic efficiency, excellent cycling stability (capacity decay of ~ 0.09% per cycle for 500 cycles), small polarization and good rate performance, significantly exceeding the performance of S/TiO 2 and S/activated carbon cathodes with similar/smaller S loading. We anticipate that this work will provide new avenues for more economic and environmentally friendly synthesis of various Magnéli phase metal oxides, and their exploration in LSBs and other fields. • Precise Magnéli Ti 4 O 7 microsphere synthesis by atom-economic and safe comproportionation reaction. • New mechanistic insights in the prevention of LiPS dissolution. • Outstanding performance of the Ti 4 O 7 /S cathodes with high S loading (~ 70%). • Generality of the synthesis is shown for other Magnéli phases.